The pressure cooker has established itself for many years in many households as an important cooking tool, because it clearly shortens the cooking time of many dishes. It saves energy costs and preserves the vitamins in the food. The pressure cooker is usually a special thick-walled pot. The upper edge is bent outwards and comprises bayonet-like recesses for receiving the pot cover, whereby a pressure-resistant connection is formed. The cover is specially shaped. The cover comprises a rubber ring gasket and usually a control valve as well as a safety valve to limit the pressure. The valves of modern pressure cookers are firmly integrated into the cover. The working valve usually uses a pin with ring markings as a pressure gauge, whereby the pin rises with rising pressure. Nowadays the valve is coupled to the locking means of the cover. To prevent accidents, the pressure cooker can only be opened after the pressure has been released. A tightly screwed cover with a safety valve closes the pot tightly.
By heating the interior of the pot to a temperature of more than 100 degrees Celsius, an excess pressure of about 1 bar can be achieved. Thereby the cooking time of most foods is significantly shortened.
DE 2832608 shows a cover for cooking pots or the like. The cover can only be used with pots or containers that show an outwardly flanged edge. With this cover it is possible to close this kind of pots or containers tightly, so that they can be used for a steam cooking method (FIG. 1A).
DE202010012194U1 describes a cover for a pressure cooker comprising a frame cover with a gasket and a handle. The cover can be locked to a special pot. The cover comprises a handle, which can be removed from the frame cover together with at least a part of the locking means (FIG. 1B).
DE 102008008311 shows a cover with an elastic ring element. The cover comprises openings for the pouring of liquids. Therefore a pressure build up is not possible and the cover cannot be used as pressure cooker (FIG. 1C).
FIG. 2 represents the pressure ratios achieved or used during cooking. The numbers correspond to the extra pressure that is built up in the respective pots. Number A shows the pressure ratios in low pressure cookers of type I, whereby only a low additional pressure is build up. In this case a pressure of up to 5 kPa over the standard pressure is built up. This additional pressure does not need to be released before the cover can be opened. In particular, up to an additional pressure of about 2 kPa the cover can be opened safely. Number B shows the pressure ratios in low pressure cookers of type II, whereby an additional pressure of about 35 kPa to 55 kPA is build up. This pressure has to be release before a type II pressure cooker can be opened. Number C shows the pressure ratios in high pressure cookers. The American standard high pressure cooker usually uses an additional pressure of about 107 kPa. Therefore a pressure of about 2 bar prevails in these pots.
A particular disadvantage of the known devices is, in particular, that these generally consist of a combination of a pot with a matching cover. Alternatively the cover can only be used with pots of almost the same diameter and with a similar shape of the upper edge.
The object of the invention is to provide a universal cover, which is adaptable to various pot sizes. The cover should furthermore be suitable for use as a low pressure cooker in combination almost any pot.
The above object is achieved by a pot cover with the features described in patent claim 1. Further advantageous embodiments are described by the dependent claims.